I wrote this in Alpha version 1 where this plays as it should. When playing in Alpha version 2, there is a strange fluttering sound that I have found is not due to the buffer or having too many instruments. If I turn the whole drum rack / machine off the flutter goes away. This is quite strange as if I individually turn off each and every drum track the flutter stays (the already well within green CPU load reduces but not as much and I have created other projects with more CPU load without the problem).